Hard disks to be incorporated into magnetic disk storage devices such as a computer have been steadily made more compact and increased in capacity, and so hard disk substrates are required to be of extremely high-precision quality. To this end, the surface of a hard disk substrate is conventionally polished for smoothing, and the process therefor includes rough polishing using alumina abrasive grains and final polishing using colloidal silica abrasive grains.
When such alumina abrasive grains used during the rough polishing are unfortunately left on the substrate surface and they are not removed even after the final polishing, characteristics of the hard disk substrate as a medium may be degraded.
To cope with this, in a known method, rinsing is provided between the rough polishing and the final polishing to rinse a hard disk substrate with rinsing solution containing colloidal silica abrasive grains, thus reducing the remaining alumina on the substrate surface. See JP Patent Publication (Kokai) No. 62-208869 A (1987).
Patent Document 1: JP Patent Publication (Kokai) No. 62-208869 A (1987)